ActaPhysica Blog

Nightwatch: A Practical Guide to Viewing the Universe

AProbot — Mon, 19 Jul 2010 07:30:54 +0000

Nightwatch: A Practical Guide to Viewing the Universe

With 250,000 copies in print since its initial publication in 1983, NightWatch has become a standard reference guide for stargazers throughout North America. The new Third Edition expands on that success with a completely revised and updated text, more than 100 new color photos and diagrams and 16 additional pages that cover such! new astronomical pursuits as computerized telescopes, reviews of new telescope designs and accessories, and astronomy on the Internet. All charts, tables and

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Scanning electron microscopy – Wellcome Image Awards 2009 (HD)

AProbot — Mon, 19 Jul 2010 07:27:28 +0000

Electron microscopes use a beam of electrons rather than photons of light to generate images from their subjects. Watch this video to see how a scanning electron microscope is used to image objects that may only be a few nanometres in thickness. For more information see www.wellcomeimageawards.org

The dependence of star formation activity on environment and stellar-mass at z~1 from the HiZELS H-alpha survey. (arXiv:1007.2642v1 [astro-ph.CO])

AProbot — Mon, 19 Jul 2010 06:31:22 +0000

(Abridged) This paper presents an environment and stellar mass study of a
large sample of star-forming (SF) galaxies at z=0.84 from the HiZELS survey,
over 1.3 deg^2 in the COSMOS and UKIDSS UDS fields. By taking advantage of a
truly panoramic coverage, from the field to a rich cluster, it is shown that
both mass and environment play crucial roles in determining the properties of
SF galaxies. The median specific SFR declines with mass in all environments,
and the fraction of galaxies forming stars declines from ~40%, for M~10^10M_sun
to effectively zero at M>10^11.5M_sun, confirming that mass-downsizing is
generally in place by z~1. The fraction of SF galaxies also falls as a function
of local environmental density from ~40% in the field to approaching zero at
rich group/cluster densities. When SF does occur in high density regions, it is
merger-dominated and, if only non-merging SF galaxies are considered, then the
environment and mass trends are even stronger and largely independent, as in
the local Universe. The median SFR of SF galaxies is found to increase with
density up to intermediate (group or cluster outskirts) densities; this is
clearly seen as a change in the faint-end slope of the H-alpha LF from steep
(-1.9), in poor fields, to shallow (-1.1) in groups and clusters.
Interestingly, the relation between median SFR and environment is only found
for low to moderate-mass galaxies (below ~10^10.6M_sun), and is not seen for
massive SF galaxies. Overall, these observations provide a detailed view over a
sufficiently large range of mass and environment to reconcile previous
observational claims: mass is the primary predictor of SF activity at z~1, but
the environment, while enhancing the median SFR of (lower-mass) SF galaxies, is
ultimately responsible for suppressing SF activity in all galaxies above
surface densities of 10-30 Mpc^-2 (groups and clusters).

astro-ph updates on arXiv.org

Cages Change Mice Brains, Lab Studies Questioned

AProbot — Mon, 19 Jul 2010 01:26:00 +0000

Research results may not be trustworthy.
Livescience.com

Pushing Electrons: A Guide for Students of Organic Chemistry

AProbot — Sun, 18 Jul 2010 22:31:16 +0000

Pushing Electrons: A Guide for Students of Organic Chemistry

SpartanModel replaces the plastic models used by past generations of organic chemistry students. This set of easy-to-use digital builders allows you to construct and manipulate 3-D molecules of any size or complexity.

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Self-assembly of nanostructures, Part 2

AProbot — Sun, 18 Jul 2010 19:30:40 +0000

Research presentation by Vladimir Dobrokhotov
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Light Colored Scalar as Messenger of Up-Quark Flavor Dynamics in Grand Unified Theories. (arXiv:1007.2604v1 [hep-ph])

AProbot — Sun, 18 Jul 2010 19:23:06 +0000

The measured forward-backward asymmetry in the t tbar production at the
Tevatron might be explained by the additional exchange of a colored weak
singlet scalar. Such state appears in some of the grand unified theories and
its interactions with the up-quarks are purely antisymmetric in flavor space.
We systematically investigate the resulting impact on charm and top quark
physics. The constraints on the relevant Yukawa couplings come from the
experimentally measured observables related to D0–D0bar oscillations, as well
as di-jet and single top production measurements at the Tevatron. After fully
constraining the relevant Yukawa couplings, we predict possible signatures of
this model in rare top quark decays. In a class of grand unified models we
demonstrate how the obtained information enables to constrain the Yukawa
couplings of the up-quarks at very high energy scale.

hep-ex updates on arXiv.org

Station Altitude Raised; Spacewalk Preps and Science Activities Continue

AProbot — Sun, 18 Jul 2010 15:23:41 +0000

The altitude of the International Space Station was raised early Friday morning after the docked Progress 38 vehicle fired its thrusters for nearly 18 minutes. The reboost places the station at an altitude to support the departure of the Expedition 24 crew in September and the arrival of the Expedition 25 crew in October.

The first Expedition 24 spacewalk will begin on Monday, July 26. Russian flight engineers Mikhail Kornienko and Fyodor Yurchikhin will exit the International Space Station� [...]

International Space Fellowship

The Nature of Space and Time [VHS]

AProbot — Sun, 18 Jul 2010 13:36:22 +0000

The Nature of Space and Time [VHS]

Einstein said that the most incomprehensible thing about the universe is that it is comprehensible. But was he right? Can the quantum theory of fields and Einstein’s general theory of relativity, the two most accurate and successful theories in all of physics, be united in a single quantum theory of gravity? Can quantum and cosmos ever be combined? On this issue, two of the world’s most famous physicists–Stephen Hawking (A Brief History of Time) and Roger Penrose (The Emperor’s New Mind and Sha

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Generation of coherent states of photon-added type via pathway of eigenfunctions. (arXiv:1007.2418v1 [quant-ph])

AProbot — Sun, 18 Jul 2010 08:25:58 +0000

We obtain and investigate the regular eigenfunctions of simple differential
operators x^r d^{r+1}/dx^{r+1}, r=1, 2, … with the eigenvalues equal to one.
With the help of these eigenfunctions we construct a non-unitary analogue of
boson displacement operator which will be acting on the vacuum. In this way we
generate collective quantum states of the Fock space which are normalized and
equipped with the resolution of unity with the positive weight functions that
we obtain explicitly. These states are thus coherent states in the sense of
Klauder. They span the truncated Fock space without first r lowest-lying basis
states: |0>, |1>, …, |r-1>. These states are squeezed, are sub-Poissonian in
nature and are reminiscent of photon-added states at Agarwal et al.

quant-ph updates on arXiv.org